docs: def compute_master(context):
      """Computes master key from transformed key and master seed.
      Used in payload decryption."""
  
      # combine the transformed key with the header master seed to find the master_key
      master_key = hashlib.sha256(
          context._.header.value.dynamic_header.master_seed.data +
          context.transformed_key).digest()
      return master_key